1. Field of the Invention
The present invention relates to a pharmaceutical composition, particularly an antirachitic agent, containing as an active ingredient 24,25-dihydroxycholecalciferol [that is, 24,25-dihydroxyvitamin D.sub.3 : hereinafter abbreviated to as "24,25-(OH).sub.2 -D.sub.3 " or "the present active substance"]. More particularly, the present invention relates to a method for treating vitamin D resistant rickets.
2. Description of the Related Art
Rickets has recently become a relatively rare disease, but intractable rickets continues to occur at a high frequency. For example, vitamin D resistant rickets often offers difficulty in treatment. Almost all the vitamin D resistant rickets suffers from a congenital metabolic disorder inherited from the X-chromosomal dominant inheritance. The initial symptoms are bowlegs and a waddling gait. Further, it is believed that the vitamin D resistant rickets is characterized in that other abnormalities are not observed in general state and depression in myodynamia or the like is not observed either, unlike other types of rickets. Pathophysiology thereof still remains unknown in many points. Although administration of vitamin D in a large amount was performed in treating vitamin D resistant rickets, improvement thereof was considered difficult (for example, see Dorland's Illustrated Medical Dictionary, Hirokawa Shoten, 1980, p. 1611). Further, a large amount of 1.alpha.-hydroxycholecalciferol [hereinafter abbreviated to as "1.alpha.-(OH)-D.sub.3 "], 1.alpha.,25-dihydroxycholecaliferol [hereinafter abbreviated to as "1.alpha.,25-(OH).sub.2 -D.sub.3 "], vitamin D.sub.2, neutral phosphate, or the like was used.
However, it is widely known that 1.alpha.,25-(OH).sub.2 -D.sub.3, 1.alpha.-(OH)-D.sub.3, vitamin D.sub.2, neutral phosphate, or the like brings about many side effects. That is, hypercalcemia occurs frequently, and long term administration causes nephrocalcinosis. Further, it have been reported in many articles that hyperparathyroidism is induced, and renal calculus is formed by urine containing excessive oxalate mainly produced by the administration of neutral phosphate, and the like (for example, see Internal Medicine, Vol. 69, No. 4, pp. 687 to 690, 1992). Therefore, in view of the serious problem of side effects in treating vitamin D resistant rickets, there has been a desire for developing a more effective and safer therapeutic medicine which is free of such side effects.